Overview

Prior self-injurious thoughts and behaviors (SITBs) are often identified as some of the most robust predictors of future SITBs. Among SITBs, suicide attempt history is consistently cited as one of the strongest risk factors for future suicidal behaviors (Fawcett et al., 1990; Joiner et al., 2005). This claim has become widely-accepted and highly influential – for instance, a recent World Health Organization (2014) report stated that “by far the strongest risk factor for suicide is a previous suicide attempt.” Supporting this position, a large body of research has consistently linked suicide attempt history to later suicidal ideation (Miranda et al., 2012; Links et al., 2012), attempts (Borges et al., 2008; O’Connor et al., 2013), and death (Suokas et al., 2001; Wenzel et al., 2011). Some studies cite over a 70-fold increase in the likelihood of a subsequent attempt (Sanchez-Gistau et al., 2013) and close to a 40-fold increase in the likelihood of death (Harris & Barraclough, 1997). However, in stark contrast to these findings, several studies have reported substantially smaller (Wenzel et al., 2011; Van Dulmen et al., 2013) or non-significant effects (Tejedor et al., 1999; Brådvik & Berglund, 2009). These discrepancies raise doubt about the true effect of prior suicide attempts on future suicidal thoughts and behaviors.

There also is disagreement about the effects of other SITBs – namely, suicidal ideation, suicide plans, features of prior attempts, and non-suicidal self-injury (NSSI) – on future suicidal thoughts and behaviors. The effects of indirect experiences with suicidal thoughts and behavior, such as a family history of suicidal thoughts and behaviors and exposure to the suicidal thoughts and behaviors of others (e.g., family, peers, etc.), also are unclear.

Given all of these inconsistencies in the literature: What are the effects of prior SITBs on future suicidal thoughts and behaviors? The present meta-analysis addresses this crucial question and includes four primary aims:

First, we provide a descriptive summary of the existing longitudinal literature addressing this question.

Second, we examine what, if any, effects prior SITBs, features of prior SITBs, family history of SITB, and exposure to SITBs have on future suicidal ideation, attempts, and death.

Fourth, we consider these findings in the context of their clinical utility, quantified as: (1) improvement in diagnostic accuracy above chance and (2) odds ratios considered in terms of absolute risk of suicide ideation, attempts, and death.

WHAT'S BEEN DONE SO FAR?

Answer: The first longitudinal study was published in 1965. Since then, a total of 172 qualifying studies have been published. Together, these studies yielded nearly 500 instances where a SITB variable was used to predict suicide ideation, attempts, or death. Most studies involved long follow-up periods (about 7 years on average), and less than 1% of studies had follow-ups of one month or less. The majority of cases involved either self-injurious (43%) or clinical samples (38%); only 19% involved general population samples. About 20% of cases involved adolescent samples. The most common outcome was suicide attempt (48%), followed by death (40%), and then ideation (12%).

Sample Severity

Follow-Up Length

Sample Age

WHAT ARE THE EFFECTS OF PRIOR SITBs?

Answer: Prior SITBs are statistically significant risk factors for suicide ideation, attempts, and death; however, effects were a lot weaker than we'd anticipated. Overall weighted mean odds ratios for ideation and attempts were only slightly above 2.0; for death, the estimate was near 1.5. Adjusting for publication bias further reduced estimates.

In addition to overall predictive power, we also evaluated the effects of specific SITB risk factor categories. Here are a few highlights:

Prior suicide ideation was the strongest predictor of ideation; NSSI and suicide attempt history were the strongest risk factors for suicide attempts; suicide attempt history, suicide ideation, and suicide plans were the strongest predictors of death.

Features of prior attempts (e.g., number, lethality, intent, preparations, recency, etc.) were rather weak, and in many case non-significant, predictors of ideation, attempts, and death.

Family history of SITB was a significant but weak predictor of both ideation and attempts and did not predict death.

Exposure to SITB significantly predicted attempts and ideation but, again, the magnitude of the effect was small.

Note. The graphs above display the results of risk factory category analyses on outcomes of suicide ideation, attempts, and death. Estimates are weighted mean odds ratios. Non-significant results are represented using gray bars. Estimates are not reported for analyses involving 3 or fewer cases, as the small number of cases compromise the reliability of estimates; Risk factor categories with fewer than 3 cases are not displayed in the graphs.

Did any Factor Moderate the effects?

Answer: Surprisingly, no -- for the most part, effects were consistent regardless of sample severity, sample age groups, or study follow-up lengths.

What's the Clinical Utility of PRIOR SITBs as predictors of future SuicidE Ideation, Attempts, and Death?

Answer: We evaluated clinical utility on two domains.

First, we looked at the improvement of diagnostic accuracy statistics. Here, we found that knowledge about SITB history offered only very slight improvement above chance prediction.

Second, we looked at the magnitude of estimates in terms of absolute risk of suicide ideation, attempts, and death. To do that, consider the following:

The likelihood of death by suicide in the United States in a given year is 12.5/100,000 (i.e., 0.000125); attempts are estimated to be 25 times more likely (i.e., 0.0031).

Based on this estimate, the presence of NSSI would still only increase the odds of an attempt to 0.013 – a figure still nearly zero.

Also, these calculations are based on prediction over a one year interval; most clinicians are tasked with determining risk over a period of days or weeks.

Taken together, our findings suggest that, in terms of absolute (rather than relative) odds, prior SITBs are weak risk factors for future suicide ideation, attempts, and death at least within the narrow methodological confines in which they have been studied to date.